At around 16:10 on Monday, January 1st, an earthquake with a magnitude of 7.6 and a maximum seismic intensity of 7 (Reiwa 6 Noto Peninsula Earthquake) occurred with its epicenter in the Noto region of Ishikawa Prefecture.
The number of earthquakes with strong shaking had been increasing before and after this earthquake, but three days after the earthquake, the number of earthquakes has gradually decreased. No expansion of the epicenter area was observed. We will summarize the activities until 20:00 on the 4th (Thursday).
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Strong earthquakes are gradually decreasing
Earthquake MT diagram including earthquakes with a maximum seismic intensity of less than 1
Earthquakes of magnitude 4 to 5 are frequently occurring after 4:00 p.m. on the 1st (Monday). As of 20:00 on the 4th (Wednesday), at least 168 earthquakes with a seismic intensity of 3 or higher have been observed, of which at least 14 earthquakes with a maximum seismic intensity of 5 lower or higher have been observed (on the 1st, provisional and preliminary figures are mixed, Figures from the 2nd onwards are preliminary figures).Today, the 4th (Thursday), three earthquakes with a maximum seismic intensity of 4 occurred, but there were no earthquakes with a seismic intensity of 5 lower or higher.
Looking at the scatter diagram (MT diagram) that shows the magnitude and time series of earthquakes, although the number of earthquakes with a magnitude of 3 or more is gradually decreasing, three days later today, earthquakes of around M5 still occur sporadically. You can see that
Looking at the distribution of the series of earthquakes, we can see that the earthquakes are not limited to the area at the northeastern tip of the Noto Peninsula, where earthquake swarms have frequently occurred since December 2020, but have spread over an area of about 150 km from the west coast of the Noto Peninsula to near Sado Island. You can see that there are. However, the epicenter area has not expanded since the day after the major earthquake, and it appears that activity has increased within the same epicenter area.
The M7.6 earthquake that occurred at 4:10 p.m. on the 1st (Monday) was much larger than previous earthquakes, so it is thought that the destruction of the bedrock caused by fault activity was widespread. For some time to come, we will need to be careful about both the intense shaking caused by the earthquake directly beneath the Noto Peninsula and the possibility of tsunamis caused by offshore earthquakes.
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Earthquakes with a seismic intensity of class 5 or higher may continue
Regarding the seismic activity that has been continuing since 2020 around the Noto Peninsula, the largest earthquake so far was an M6.5 earthquake with a maximum seismic intensity of 6+ on May 5, 2023, but this M7.6 earthquake is one of the 30th to 30th. That’s about 60 times more energy. Looking at the earthquakes that have occurred around Japan, excluding deep earthquakes, this is the largest earthquake since the Tohoku Pacific Coast Earthquake in March 2011.
This is the first time a seismic intensity of 7 has been observed in Japan since the 2018 earthquake in the central-eastern Iburi region, and other earthquakes that caused major damage include the Kumamoto Earthquake, the Tohoku Pacific Coast Earthquake that caused the Great East Japan Earthquake, and the Niigata Prefecture Chuetsu Earthquake. It’s all about things. This is the first time since observations began that a seismic intensity of 7 has been observed within Ishikawa Prefecture.
Although the number of earthquakes is expected to gradually decrease in the future, the probability of a strong earthquake occurring will continue to be much higher than in normal times for some time. If the building has been damaged so far, there is a risk that it will collapse in a subsequent earthquake, so please continue to stay in a safe place.
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In Shiga Town, which was hit by an earthquake with a magnitude of 7, there were reports of buildings collapsing and cracks appearing on roads. According to the fire department and police, five people have been confirmed dead in Ishikawa Prefecture as of 6:00 a.m. on the 2nd (Tuesday). It is said that there are still many people who have not been contacted, and it may take some time before the full extent of the damage is revealed.
Overview of the series of largest earthquakes
Epicenter: Noto region, Ishikawa prefecture
Scale (magnitude): M7.6
Depth of epicenter: 16km
Seismic intensity in various places (seismic intensity 6 lower or higher)
■Seismic intensity 7:
[Ishikawa Prefecture]Kano, Shiga Town
■Seismic intensity 6+:
[Ishikawa Prefecture]Kakiyoshi-cho, Nanao City, Mukoda-cho, Notojima, Nanao City, Houji-cho, Wajima City, Kawai-cho, Wajima City, Misaki-cho, Suzu City, Shoin-cho, Suzu City, Otani-cho, Suzu City, Omachi, Anamizu-cho
■Seismic intensity 6 lower:
[Niigata Prefecture]Nakanoshima, Nagaoka City
[Ishikawa Prefecture]Shiga Town, Togiryoke Town, Shiga Town, Sueyoshi Chifuru, Nanao City, Honfuchu Town, Nanao City, Sodegae Town, Nakanoto Town, Suesaka, Nakanoto Town, Noto Shita, Noto Town, Ushitsu
Due to this earthquake, a major tsunami warning was issued for Ishikawa Prefecture and a tsunami warning for the Hokuriku region and other areas, but both were canceled as the earthquake weakened over time.
The height of the observed tsunami at Wajima Port, the largest port, was announced to be “1.2 meters or more,” but the exact maximum height is not known at this time.
source
Epicenter distribution data: From the Japan Meteorological Agency website
Reference materials etc.
2024-01-04 12:40:00
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